An international hallmark
The Convention on the Control and Marking of Articles of Precious Metals, signed in Vienna in 1972 and usually called the Hallmarking Convention, created the first international hallmark: the Common Control Mark, or CCM. A designated assay office in a Contracting State applies it after testing the article’s fineness by the Convention’s agreed methods. Every other Contracting State then accepts that article without testing or marking it again, provided its fineness is legal there.
The CCM is a conformity mark. It does not say where an article was made or who made it; it says that an assay office working to the Convention’s standards tested it and found it to be the fineness shown. It is protected under the Paris Convention for the Protection of Industrial Property and published in the World Intellectual Property Organization’s Article 6ter database, which is why imitating it is a trademark matter as well as a hallmarking one.
What sits beside it
A CCM never appears alone. In its original form, Type 1, the mark sits in a shield whose shape tells you the metal — platinum, gold, palladium and silver each have their own — and it carries the fineness in parts per thousand. It is struck together with the mark of the assay office that tested the piece and a responsibility mark, called a sponsor’s mark in the United Kingdom, that identifies who submitted it. The Convention describes those three marks as compulsory when applied together.
In 2019 the Convention introduced a Type 2 CCM with one standard octagonal shield for every metal. Because the shield no longer shows the metal, a Type 2 mark is applied with five marks in all: the CCM, the assay office mark, the responsibility mark, a mark for the precious metal and a fineness mark. Some of those can be combined, such as an assay office mark that also shows the metal.
The finenesses, and the five everyone accepts
The Type 1 CCM exists in these finenesses, in parts per thousand: platinum 999, 950, 900 and 850; gold 999, 916, 750, 585 and 375; palladium 999, 950 and 500; silver 999, 925, 830 and 800. For gold, 750 and 375 are exactly 18 and 9 karat; 916 and 585 are the millesimal standards used for 22 and 14 karat, which as exact fractions of 24 would be 916.7 and 583.3.
A CCM fineness is not automatically saleable in every member country. Each Contracting State still decides which finenesses are legal within its own borders, and accepts CCM-marked goods only in a fineness that is legal there. The Convention names five that are legal in every Contracting State: platinum 950, gold 750, gold 585, silver 925 and silver 800. Palladium, added in 2010, is not accepted everywhere. Secondary sources sometimes list gold 990 among the Convention standards; the Convention’s own page does not, and neither does this one.
Who the members are
The Convention lists 22 Contracting States, the most recent being Italy, which acceded on 15 December 2023. Most are European, with Israel the member outside the continent, and the United Kingdom is among them. The list on this page is taken directly from the Convention’s members page and dated, because accessions do happen.
Membership has a practical edge for anyone looking at a mark. Because the UK is a Contracting State, an article bearing a CCM struck by another member’s assay office is accepted there as hallmarked without being sent to a British assay office. The United States is not a member and has no hallmarking system of this kind; US gold and silver marks are governed by the National Gold and Silver Marking Act instead.
What a CCM does not tell you
A CCM confirms fineness. It says nothing about weight, about the quality of workmanship, about stones set in the piece, or about what the article is worth. Like any hallmark it can be forged, and the usual checks apply: the marks should be crisp, struck rather than cast, and consistent with one another. Melt value follows from the fineness and the weight; resale value is a separate question that the mark does not answer.